The present invention relates to a camera of the type having a taking lens system which can be changed suitably for wide-angle photography or telephotography by changing the focal length thereof.
Numerous compact cameras having lens shutters are provided with taking lens systems of the type in which the focal length can be changed between a relatively short focal length of, for example, about 35 mm suitable for wide-angle photography and a relatively long focal length of, for example, 70 mm suitable for telephotography. For changing the focal length of the taking lens system in such a camera, an extra lens, such as a conversion lens, is provided which is displaced from the optical path of the taking lens when the taking lens system is changed to short focal length and, on the other hand, is moved into the optical path simultaneously with the axial movement of the main focusing lens, such as a master or objective lens, of the taking lens when changing to long focal length
In many cases, the angle of view and the lens speed (F-number) of the taking lens system will change upon changing the taking lens system between two different focal lengths. It is accordingly necessary to effect exposure control in different ways, depending on whether the lens system is set for wide-angle photography or telephotography.
For different exposure controls, such cameras are equipped with exposure control meters which have a diaphragm or stop member disposed in front of a photoelectric element to changeably control the quantity of light reaching the photoelectric element according to the lens speed of the taking lens system. In addition, such an exposure control meter coacts with an axially movable cylindrical barrel disposed between a light entering window and the photoelectric element to change the angle at which incident light falls on the photoelectric element according to the changed angle of view of the taking lens system.
The provision of such a stop member and an incident angle changing member with their associated elements leads to a complication of the structure of the focal length changeable camera.